This one's rather simple. Build a reservoir into a dishwasher attached to a meter long hose with a nozzle on the end. The hose is normally clipped to the top of the dishwasher, just inside the door. Then fill the reservoir with a harmless black fluid that is very easy to wash off of dishes. A very
thin mud may work. As you load dirty dishes into the washer spray them with the fluid so it is very obvious that they are DIRTY. All of the mud will be removed during the wash so any dishes that appear clean will actually be clean. This also allows you to mix clean and dirty dishes - just mark the dirty ones as you put them in and take out the clean ones.

I like the idea of having two dishwashers better. Start with one full of clean dishes. Put sign on it saying CLEAN. Then start using those dishes, and when they are dirty, put them into the other dishwasher, the one without the sign.

When the first one is emptied, the second one is full, so run the cleaning cycle and move the sign. You never need to use the dish-cabinets on the wall for that purpose.

This liquid, if composed correctly, might actually help prevent food from drying on or even loosen baked on food, kind of like stain stick but for dishes. Sell it in an aerosol can so people can try this out without the expense of installing a spray nozzle. It can be conveniently stored in the dishwasher when it's not running.